Over the last twenty years, much work has been performed in the ASTM task groups of D11.12 Subcommittee on Rubber Processability Measurements with the Rubber Process Analyzer (RPA). As a result, nine new standards have been developed and routinely used by the rubber industry.
Key takeaways
- Developed in ASTM D11.12, the Subcommittee on Rubber Processability Measurements
- Used worldwide to test raw elastomers and to measure and control masterbatches and finals, with curatives
- They cover frequency sweeps, VTA, cure plus strain sweeps, stress relaxation, Payne effect and TPV/TPE testing
These standards are routinely used by the rubber industry to test different raw elastomers and to measure and control compound masterbatches and finals, with curatives, from various mixing processes all over the world.
The standards
RPA Standards at a Glance
| ASTM standard | What it covers |
|---|---|
| D5289 | The original MDR curemeter standard on which a significant amount of modern day RPA technology is based. |
| D6204 Part A | Simple 1 point per decade frequency sweep at ±7% strain (usually in the linear viscoelastic range) at 100 °C for testing either raw rubbers or mixed stocks in the factory. |
| D6204 Part B | Simple 2 point frequency sweep at 0.1 and 1 Hz at ±100 and/or ±200% strain at 100 °C for testing in the non-linear viscoelastic range for either raw rubber or mixed stocks in the factory. |
| D6204 Part C | A variable temperature analysis (VTA) thermal ramp typically from 100 to 180 °C, for better test sensitivity to changes in scorch safety for “finals” (uncured compounds containing curatives). |
| D6601 | An isothermal cure test followed by one or two back-to-back strain sweeps to quickly measure cured dynamic properties of the rubber compound at a lower temperature. |
| D7050 | High strain sweep tests to quickly distinguish the differences between “tough” natural rubber and “soft” natural rubber. |
| D6048 | A stress relaxation test for quickly determining the state-of-mix of a mixed stock or viscoelastic characterization of raw rubber in regards to AMW, MWD, LCB, and gel. |
| D8059 | Using the RPA with Extended Dynamic Range (EDR™), after a conditioning time, starting with a very low applied strain at ±0.07% and increasing quickly to ±300%, measuring the Payne effect for quickly determining the state-of-mix and % dispersion of a rubber compound filled with a colloidal particle size filler such as carbon black or precipitated silica. |
| D7605 | Using the RPA with parallel plate dies to measure both the processing characteristics and congealed properties of Thermoplastic Vulcanizates (TPVs) and Thermoplastic Elastomers (TPEs). |
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The Premier RPA and Premier MDR run these methods for raw elastomers, masterbatches and finals.